242 DIPTERA OP NORTH AMERICA. [PART IV. 



the shortness of its valves ; the upper pair is always shorter than 

 the rather obtuse lower pair. 



Anisomera is ; among all the Tipulidse, the only genus which 

 has three posterior cells (and this venation is still more reduced 

 in the genus Cladolipes Loew, which has only one submarginal 

 cell). Nevertheless, the relationship of Anisomera to Eriocera 

 (with its four or five posterior cells) cannot be called in doubt. 

 The anomalous structure of the antennae, the great length which 

 they frequently attain in the male, the structure of the head and 

 of the feet prove this relationship. 



Hitherto I have discovered only one North American species 

 of Anisomera ; it is distinguished by the considerable length 

 of its antennae. Mr. Loew enumerates nine European species. 

 One of them, A. fuscipennis, has been proposed, by Mr. Curtis 

 (Brit. Entom. 539 ; 1836), for the type of a separate genus, 

 Peronecera (from /tspovq, a button, and *fpaj, horn, in allusion to 

 the rudimental joint at the tip of the antenna?). This genus, also 

 adopted by Loew, is based solely upon the number of antennal 

 joints, which is seven in the male and nine in the female (this is 

 Mr. Loew's statement; Mr. Curtis says seven (%) and eight 

 joints ( 9 )). The antennae are short in both sexes, and not much 

 longer in the male than in the female. According to Mr. Loew, 

 Peronecera is closely related to those Anisomerse with short male 

 antennae, which have a rudimental seventh joint. Such species 

 have but a limited power of flying, as they seem to jump rather 

 than to fly (Loew, 1. c. p. 414). Mr. Loew mentions but a single 

 species of Peronecera ; Mr. Curtis, besides this same species, 

 describes another one, P. lucidipennis, n. sp. 



The species of Anisomera occur along the banks of streams ; 

 the larvae (according to Yan Roser (Verz. Wurt. Dipt. p. 262) 

 live in the sand of these banks (or perhaps in the vegetable de- 

 tritus found there ?). 



The first species belonging to this genus was described by 

 Latreille, in 1809 (Genera Crust, et Ins. IV, p. 260), under the 

 generic name of Hexatoma. 



Meigen, in 1818, rather arbitrarily changed the name of Hexa- 

 toma in Nematocera, on the ground that he had been compelled 

 to alter the name of his own genus Heptatoma (Tabanidae) in 

 Hexatoma (Meig. Yol. I, p. 209). At the same time he adopted 



